Authorities said Dittmeyer -- who lives in Portland, Maine, and is considered missing and endangered -- last talked to family members by phone at around 8 p.m. Friday.

Police received a call from a passerby at around 6:30 a.m. Saturday who reported Dittmeyer's car in the Cranmore Mountain resort parking lot in Conway, N.H., with its hazard lights blinking and door slightly ajar. The young woman's 14-month-old daughter was unharmed in the back seat, but Dittmeyer was nowhere to be found.

Perley said he does not believe Dittmeyer left her car willingly.

"From a very early point in the investigation we drew the conclusion that she did not voluntarily absent herself from her car," he said during an interview.

Perley said one of the vehicles police are searching is Dittmeyer's. He declined to comment further on the second vehicle being investigated.

Carroll County Sheriff Christopher Conley reportedly told the New Hampshire Union Leader that "blood evidence" was found inside Dittmeyer's vehicle. Perley would not confirm the report with FoxNews.com, saying the Conway Police Department "does not to comment on specific pieces of evidence."

Perley said police don't know why Dittmeyer drove to Conway but noted that the young woman had a "number of social contacts" in the area.

The woman's sister, Kayla Dittmeyer, told the Portland Press Herald that she believes someone forced her sister out of the car and that her sister persuaded that person to leave her daughter behind.

"My sister is very headstrong, but she is also very bold and very honest. That is why I feel she is OK. She's a very strong person," Dittmeyer said of her sister, a single mother who works as a waitress. "I believe she is trying to talk her way through this."

"She would do anything for her," she said. "It was all so out of character for her. She would never put her daughter in harm's way."

Dittmeyer's family is offering a $3,000 reward for help finding her. A vigil is also being planned for Thursday in Bridgton, Maine, where Dittmeyer's family lives.

Anyone with information on Dittmeyer's whereabouts is being urged to call the Conway Police Department at (603) 356-5715.